The present invention relates to a method and apparatus for producing a circuitry and particularly to a method and apparatus for producing a circuitry constituted by electric conductor circuits which is formed as patterns from bus bars, electric wires, etc. in electric junction box of a wiring system on a vehicle.
FIG. 8 shows an electric junction box which is proposed by the present Applicant as an example in which a circuitry constituted by electric conductor circuits is mounted. For example, the electric junction box 1 is provided for distributing and supplying a voltage from a power supply to on-vehicle electrical components through relays 2 and fuses 3. A body of the electric junction box has an upper cover 4, a wiring board 5, and a lower cover 6. The relays 2 and the fuses 3 are inserted in connection blocks 7 and 8 respectively so as to be held and received in the upper cover 4. Patterns of electric-power supply circuits are formed from bus bars 9 on the wiring board 5. A rear surface of the wiring board 5 is connected to pressure contact terminals so that patterns of electric-power supply circuits are formed from electric wires 10. In this manner, the patterns of electric conductor circuits are formed from the bus bars 9 and the electric wires 10 on the front and rear surfaces of the wiring board 5. The wiring board 5 is received in the lower cover 6 and further assembled with the upper cover 4 from above to thereby form the electric junction box 1.
The example of the circuitry is not limited to the case where the bus bars 9 and the electric wires 10 are used as shown in FIG. 8. Generally, in the case of bus bars 9, a sheet of copper foil is processed into circuit shapes by press-cutting or the like in accordance with the wiring direction and the current-carrying capacity. In the case of specifications of electric wires 10, diameters (small or large) are selected in accordance with the current-carrying capacity and the electric wires 10 are disposed along circuit patterns.
FIGS. 9, 10A and 10B typically show an example of the circuitry constituted by electric conductor circuits of only bus bars. That is, in this example, the electric conductor circuits constituted by a plurality of bus bars 12 to 16 different in width and length are formed as patterns on an insulation substrate 11. FIG. 10A is a sectional view taken along the line C—C in FIG. 9 and showing one bus bar 12. FIG. 10B is a sectional view taken along the line D—D in FIG. 9 and showing another bus bar 13 different in size from the bus bar 12.
The examples of the circuit bodies shown in FIGS. 8, 9, 10A and 10B have the following problems.
In the case of the circuitry shown in FIG. 8, electric wires with diameters of various specifications are used for forming patterns. Hence, there is a disadvantage in that the circuitry becomes heavy in weight. Moreover, it is necessary to fix terminals by some fixing method such as adhesion after electric wires cut into different sizes are disposed. In addition, the cost of production becomes high because the troublesome operation step of binding several electric wires 10 with a tape is required.
In the case of the circuitry shown in FIGS. 9, 10A and 10B, after bus bars 12 to 16 different in size and shape are formed from a sheet of copper foil by press cutting, the residual material of the copper foil is discarded as waste or subjected to a recycling process to attain reclamation. Hence, when a complex circuitry is formed as patterns from bus bars, it cannot be always said that the yield of material is good. In addition, like the case of the electric wires, it is necessary that the bus bars 12 to 16 obtained thus as materials are fixed onto the insulation substrate 11 by a fixing method such as adhesion. Hence, this is also a cause of increase in cost.
Particularly in vehicles and various kinds of electric/electronic apparatuses severely limited in reduction of weight and wiring space, FPCs (flexible printed circuit boards) and FFCs (flexible flat circuit boards) capable of being applied flexibly thereto is used popularly to solve the problems in such a circuitry using bus bars or electric wires as described above. In recent years, however, the arrangement space and wiring space is limited more severely with the increase in the number of functions and the increase in the number of circuits caused by increase in the number of peripheral apparatuses. That is, in the existing environment, it has become impossible to use even the FPCs and FFCs as wiring circuits and wiring boards. Moreover, in each of the FPCs and FFCs, electric conductor wiring needs to be covered with an insulation film to form an insulation structure. In addition, it is uneconomical to use the FPCs and FFCs because redundant portions are removed by fusion or another method.
As described above, the circuit bodies using bus bars, electric wires, FPCs and FFCs have the problems respectively. In recent years, in place of those circuit bodies, a method of flame spraying a metal rod or metal powder by plasma or arc while spraying nitrogen gas or the like to thereby spray molten metal onto a target position has begun to be used. In the method of spraying molten metal, a process such as masking sealing is required for spray-depositing molten metal on the target position accurately. Hence, there is a disadvantage in that the cost for processing material becomes correspondingly high. In addition, a large amount of molten metal is diffused into a wide range, so that there arises a problem that it is uneconomical to use the method because the material is wasteful.